How U.S. Researchers Are Making the Switch to the Large Hadron Collider

To unlock new secrets of the universe, Stephanie Majewski has to brush up on her French. The 27-year-old particle physicist is part of an international collaboration working on ATLAS, one of two experiments the size of small apartment buildings that will soon come online near Geneva, Switzerland.

Majewski, a postdoctoral fellow at Brookhaven National Laboratory in Upton, N.Y., knew when she got her PhD last year that she wanted to work on the Large Hadron Collider (LHC), the circular particle accelerator 17 miles (27 kilometers) in circumference straddling the Franco-Swiss border.

In coming months, the LHC will begin to slam together twin beams of protons at the highest energies ever achieved in a science experiment. ATLAS and CMS are the two main particle detectors designed to sift the debris, looking for the long-awaited Higgs boson and other elusive quarry.

"It's the place to be for particle physics," she says. "This may be the last large accelerator that turns on, at least for awhile." To make herself known in a collaboration of more than 1,700 people from 37 countries, Majewski will spend the next year living in Meyrin, Switzerland, close to ATLAS and the LHC at the European Organization for Nuclear Research (CERN).

The U.S. has been home to the premier particle physics experiment, the Tevatron at Fermi National Accelerator Laboratory (Fermilab) in Batavia, Ill., for more than two decades. Now the LHC is taking up that mantle. Its imminent start-up—CERN plans to inject the first fully circulating beam through the LHC next week, followed in coming weeks by the first collisions—means a new phase in the lives of the nearly 2,000 U.S. researchers who are working on LHC experiments.

Not all of them will have to learn the French for, "no, black holes are not about to destroy the world." But as part of an international team, "the U.S. has to do its share," says Fermilab's Joel Butler, head of U.S. CMS operations.

The U.S. CMS group consists of about 130 engineers, technicians and computer scientists plus about 600 physicists and graduate students. Butler says he expects that at any given time, somewhere between 150 and 200 of them will be at CERN.

The LHC will only run for about seven months out of the year, from late spring to late December. Although the CMS detector is inaccessible during that time, a pair of control rooms—one underground, one above ground—contain much of the electronics for the experiment as well as computers for processing the data.

"Some problems can only be solved by going down into the underground control room and fiddling with the electronics or making replacements of failed components," Butler says. During the downtime from late December to March, workers may have to open the detector to fix problems or perform routine maintenance.

A typical experience for a postdoc might be to spend a year or two at CERN to speed communication within the experiment. Two other postdocs in Majewski's group are currently stationed at CERN, taking shifts in the ATLAS control room. "We have to watch to make sure that everyone in our group gets enough trips to CERN so that we all can attend meetings in person and stay connected to our collaborators," she says.

The Stanford Linear Accelerator Center (SLAC) has four postdocs working on the ATLAS experiment at CERN, along with two PhD students, one staff scientist and one co-team leader, Su Dong, co-leader of SLAC's ATLAS team, says. He recommends that young researchers spend 1.5 to two years at CERN. Although there's an added cost to moving there, extended stays end up being cheaper than many shorter trips, he says.

Having eyes and ears at CERN was definitely an advantage this year, as the lab scrambled to get the collider up and running on schedule after years of delays. "It was really important to have people there who could run into someone in the hall and get an update," Majewski says.

Once the LHC begins colliding protons, researchers will have to learn how to interpret the raw data from detectors and translate it into real physics. That's where conversations over the lunch table come into play: Talking to someone on site who knows the detectors may provide the key to interpreting a funny looking piece of data, Su Dong says. Ideally, relationships built at CERN translate to improved communication after researchers return to the U.S. "Once you get to know them it's much easier to talk to them over a remote link," Butler says.

Of course, not all institutions can afford to send researchers to CERN or take them away from teaching duties. Another option for U.S. CMS researchers who can't make the trek to Switerland is to take a shift at a remote operations center (ROC) established at Fermilab. From there, researchers can monitor day-to-day operations of the experiment and work with CERN staff to keep it running smoothly.

Historically, CERN experiments have not had remote operations, Butler says. But the CMS experiment and its control rooms are located on the far side of the LHC, about 12 miles (20 kilometers) from the main CERN campus. So the lab created a second monitoring station to allow researchers to track the experiment from the main office.

That opened the door to remote access from the U.S., Butler says: "Once you're sending information 20 kilometers, the fact that you may want to send it 5,000 or 6,000 kilometers is no different, except for bandwidth."

Fermilab had already experimented with remote access for experiments such as CDF at the Tevatron and NuTeV, a neutrino experiment. In the case of CDF, researchers from Italy, Japan, Korea and other countries would take eight-hour shifts monitoring the data from their home institutes, says Fermilab's Kaori Maeshima, who oversaw those remote operations and was tasked four years ago with implementing it for CMS.

If researchers can only participate from CERN, the experiment isn't fully utilizing its resources, Maeshima says. Team members in other countries can take shifts during their daylight hours while their counterparts at CERN are asleep.

Fermilab completed the ROC in fall 2005. It is a small-scale version of the CMS control room at CERN, complete with a 24/7 video link, called "the window to CERN." Control of the experiment is limited to the aboveground CMS detector station. Monitoring the data can take place there, at CERN's remote station or at the ROC.

"What the ROC brings us here at [Fermilab] is a center where we can congregate and be able to easily work with our colleagues at CERN to solve whatever problems we run into as we take data," says David Mason, a Fermilab postdoc who uses the remote center to confirm that data is being processed and transferred in the right way within the LHC Computing Grid. "I can monitor and work with the data from Fermilab as well as I could from CERN," he says.

The same principles apply for other nations taking part in the collaboration. Butler says the CMS team is building a remote station at the DESY lab in Zeuthen, Germany, and has seven or eight other stations planned. The ATLAS collaboration is also making plans to establish remote operations.

"Remote operations [in particle physics] has been around for awhile, but it's never been embraced this early and in quite this depth by anyone," Butler says. "It's an exciting challenge."

Those who can take advantage of the opportunity to relocate to CERN are certainly happy to do so, if Majewski is any indication. Working on the LHC has made the world seem much smaller, she says. She considers the time abroad an added bonus of being at the forefront of particle physics. "I get to spend a year in Europe," she says. "All my friends are very jealous."